Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$11.74	10.195%	$12.9369	$12.94	$12.95	$12.90
Purchase #2	$191.58	11.498%	$213.6079	$213.61	$213.60	$213.60
Purchase #3	$85.35	5.126%	$89.725	$89.73	$89.75	$89.70
Purchase #4	$195.44	10.492%	$215.9456	$215.95	$215.95	$215.90
Purchase #5	$148.40	9.373%	$162.3095	$162.31	$162.30	$162.30
Purchase #6	$39.55	10.264%	$43.6094	$43.61	$43.60	$43.60
Purchase #7	$123.39	4.278%	$128.6686	$128.67	$128.65	$128.70
7 purchase totals =	$795.45		$866.8029	$866.82	$866.80	$866.70